package club.beimeng.demos.de2021年4月14日;

import java.util.Scanner;

public class One
{
    public static void main(String[] args)
    {
        Scanner cin = new Scanner(System.in);

        int a = cin.nextInt();
        int b = cin.nextInt();

        if (a > b)
        {
            int temp = a;
            a = b;
            b = temp;
        }

        int sum = 0;
        for (int i = a + 1; i < b; i ++)
        {
            if (i % 2 != 0)
                sum += i;
        }

        System.out.println (sum);
    }
}

/*
 *
 * @author Mr.Bao
 * @date
 */